A set of compressed natural gas (CNG) multi-point direct injection system of spark-ignited engines and the corresponding measurement and data acquisition systems were developed in this paper. Based on different inject...A set of compressed natural gas (CNG) multi-point direct injection system of spark-ignited engines and the corresponding measurement and data acquisition systems were developed in this paper. Based on different injection modes, the mixture formation and combustion of CNG low-pressure direct injection (LPDI) engines were studied under varying factors such as air/ fuel ratio, injection timing. Meanwhile, three-dimensional simulations were adopted to explain the mixture formation mechanisms of CNG low-pressure compound direct injection (LPCDI) mode. On the basis of test results and simulation of the mixture homogeneous degree, the conception of injection window was proposed, and the LPCDI mode was proved to be more beneficial to the mixture concentration stratification formation in cylinder under lean-burning conditions, which resulted in effective combustion and stability.展开更多
A three dimensional model which considers the effects of turbulence and detailed chemi cal kinetics is built to simulate the combustion process of engine fueled by compressed nature gas （CNG）. The model is accompli...A three dimensional model which considers the effects of turbulence and detailed chemi cal kinetics is built to simulate the combustion process of engine fueled by compressed nature gas （CNG）. The model is accomplished by integrating CFD software KIVA3V and chemical kinetic soft- ware CHEMKINII. Meanwhile, a turbulence combustion model which is suitable for describing the reaction rate under the coupled simulation is developed to balance the effects of turbulence and de tailed chemical kinetics. To reduce the computation time, subsequent development of the simulation code is realized, which enables the simulation code to have the function of parallel computing and run on parallel computing facility based on message passing interface （MPI）. The coupled software is used to simulate the combustion process of spark ignition CNG engine. The results show that sim ulation data have a good consistency with experimental results and parallel computing has good effi ciency and accelerate ratio.展开更多
为解决在选择性催化还原技术(selective catalytic reduction,SCR)的控制策略开发中局部线性模型树(local linear model tree,LOLIMOT)排放模型预测精度不足的问题,提出一种通过优化空间边界,将原模型的超矩形输入空间约束在物理意义范...为解决在选择性催化还原技术(selective catalytic reduction,SCR)的控制策略开发中局部线性模型树(local linear model tree,LOLIMOT)排放模型预测精度不足的问题,提出一种通过优化空间边界,将原模型的超矩形输入空间约束在物理意义范围内的改进LOLIMOT模型。通过某天然气发动机的辨识试验,从分布特征和计算原理角度,分析了该方法对预测结果的影响。结果表明:与原算法相比,改进算法的线性相关度R2提升了1.9%,验证了改进策略的有效性。改进LOLIMOT算法具备较高的收敛速度和稳定性,在排放模型领域具备一定的应用优势。展开更多
Hydroxy gas (HHO) is one of the potential alternative fuels for spark ignition (SI) engine,notably due to simultaneous increase in engine performance and reduction in exhaust emissions.However,impact of HHO gas on lub...Hydroxy gas (HHO) is one of the potential alternative fuels for spark ignition (SI) engine,notably due to simultaneous increase in engine performance and reduction in exhaust emissions.However,impact of HHO gas on lubrication oil for longer periods of engine operation has not yet been studied.Current study focuses on investigation of the effect of gasoline,CNG and CNG-HHO blend on lubrication oil deterioration along with engine performance and emissions in SI engine.HHO unit produces HHO gas at 4.72 L/min by using 6 g/L of KOH in the aqueous solution.CNG was supplied to the test engine at a pressure of 0.11 MPa using an electronically controlled solenoid valve.Engine tests were carried out at different speeds at 80%open throttle condition and various performance parameters such as brake power (BP),brake specific fuel consumption(BSFC),brake thermal efficiency (BTE),exhaust gas temperature and exhaust emissions (HC,CO_(2),CO and NO_(x))were investigated.In addition,various lubrication oil samples were extracted over 120 h of engine running while topping for drain out volume and samples were analyzed as per ASTM standards.CNG-HHO blend exhibited better performance i.e.,15.4%increase in average BP in comparison to CNG,however,15.1%decrease was observed when compared to gasoline.CNG-HHO outperformed gasoline and CNG in the case of HC,CO_(2),CO and brake specific fuel consumption (31.1%decrease in comparison to gasoline).On the other hand,CNG-HHO produced higher average NO_(x) (12.9%) when compared to CNG only.Furthermore,lubrication oil condition(kinematic viscosity,water contents,flash point and total base number (TBN)),wear debris (Iron (Fe),Aluminum(Al),Copper (Cu),Chromium (Cr)) and additives depletion (Zinc (Zn),Calcium (Ca)) presented a significant degradation in the case of CNG-HHO blend as compared to gasoline and CNG.Lubrication oil analyses illustrated 19.6%,12.8%and 14.2%decrease in average viscosity,flash point and TBN for CNG-HHO blend respectively.However,average water contents,Fe,Al and Cu mass concentration appeared 2.7%,25×10^(-6),19×10^(-6),and 22×10^(-6) in lubrication oil for CNG-HHO respectively.展开更多
The regulated gaseous emissions from 2 China-V compressed natural gas(CNG)buses and 2 China-V diesel buses were investigated using a portable emissions measurement system(PEMS)under real road driving conditions.Compar...The regulated gaseous emissions from 2 China-V compressed natural gas(CNG)buses and 2 China-V diesel buses were investigated using a portable emissions measurement system(PEMS)under real road driving conditions.Compared to diesel buses,CNG buses emit less NOx pollutants,but more HC and CO pollutants based on the test results obtained in this paper.In order to evaluate the pollutant emission status of CNG buses in Beijing,an instantaneous emission model as a function of vehicle speed and vehicle specific power(VSP)was developed and validated based on emission data taken from one CNG bus.The input of the instantaneous emission model consists of driving cycle,vehicle parameters,road conditions,ambient conditions and accessory use,all of which were used to calculate the instantaneous vehicle specific power(VSP).For the core model,a group of pollutant emission maps represented as functions of vehicle speed and VSP were used to calculate the second by second emission rates.Finally,the instantaneous emission rates,emission factors and fuel consumption over the selected driving cycle could be obtained as the model outputs.The predicted results for the emissions and fuel consumption of the CNG bus were very close to the tested emission data.The prediction errors for emission factors and fuel consumption varied in the range of-1.6 2%to-5.8%.展开更多
基金Supported by National High Technology Research and Development Program ("863" Program) of China (No.2008AA11A114)
文摘A set of compressed natural gas (CNG) multi-point direct injection system of spark-ignited engines and the corresponding measurement and data acquisition systems were developed in this paper. Based on different injection modes, the mixture formation and combustion of CNG low-pressure direct injection (LPDI) engines were studied under varying factors such as air/ fuel ratio, injection timing. Meanwhile, three-dimensional simulations were adopted to explain the mixture formation mechanisms of CNG low-pressure compound direct injection (LPCDI) mode. On the basis of test results and simulation of the mixture homogeneous degree, the conception of injection window was proposed, and the LPCDI mode was proved to be more beneficial to the mixture concentration stratification formation in cylinder under lean-burning conditions, which resulted in effective combustion and stability.
基金Supported by the National Natural Science Foundation of China(50976012)
文摘A three dimensional model which considers the effects of turbulence and detailed chemi cal kinetics is built to simulate the combustion process of engine fueled by compressed nature gas （CNG）. The model is accomplished by integrating CFD software KIVA3V and chemical kinetic soft- ware CHEMKINII. Meanwhile, a turbulence combustion model which is suitable for describing the reaction rate under the coupled simulation is developed to balance the effects of turbulence and de tailed chemical kinetics. To reduce the computation time, subsequent development of the simulation code is realized, which enables the simulation code to have the function of parallel computing and run on parallel computing facility based on message passing interface （MPI）. The coupled software is used to simulate the combustion process of spark ignition CNG engine. The results show that sim ulation data have a good consistency with experimental results and parallel computing has good effi ciency and accelerate ratio.
文摘为解决在选择性催化还原技术(selective catalytic reduction,SCR)的控制策略开发中局部线性模型树(local linear model tree,LOLIMOT)排放模型预测精度不足的问题,提出一种通过优化空间边界,将原模型的超矩形输入空间约束在物理意义范围内的改进LOLIMOT模型。通过某天然气发动机的辨识试验,从分布特征和计算原理角度,分析了该方法对预测结果的影响。结果表明:与原算法相比,改进算法的线性相关度R2提升了1.9%,验证了改进策略的有效性。改进LOLIMOT算法具备较高的收敛速度和稳定性,在排放模型领域具备一定的应用优势。
文摘Hydroxy gas (HHO) is one of the potential alternative fuels for spark ignition (SI) engine,notably due to simultaneous increase in engine performance and reduction in exhaust emissions.However,impact of HHO gas on lubrication oil for longer periods of engine operation has not yet been studied.Current study focuses on investigation of the effect of gasoline,CNG and CNG-HHO blend on lubrication oil deterioration along with engine performance and emissions in SI engine.HHO unit produces HHO gas at 4.72 L/min by using 6 g/L of KOH in the aqueous solution.CNG was supplied to the test engine at a pressure of 0.11 MPa using an electronically controlled solenoid valve.Engine tests were carried out at different speeds at 80%open throttle condition and various performance parameters such as brake power (BP),brake specific fuel consumption(BSFC),brake thermal efficiency (BTE),exhaust gas temperature and exhaust emissions (HC,CO_(2),CO and NO_(x))were investigated.In addition,various lubrication oil samples were extracted over 120 h of engine running while topping for drain out volume and samples were analyzed as per ASTM standards.CNG-HHO blend exhibited better performance i.e.,15.4%increase in average BP in comparison to CNG,however,15.1%decrease was observed when compared to gasoline.CNG-HHO outperformed gasoline and CNG in the case of HC,CO_(2),CO and brake specific fuel consumption (31.1%decrease in comparison to gasoline).On the other hand,CNG-HHO produced higher average NO_(x) (12.9%) when compared to CNG only.Furthermore,lubrication oil condition(kinematic viscosity,water contents,flash point and total base number (TBN)),wear debris (Iron (Fe),Aluminum(Al),Copper (Cu),Chromium (Cr)) and additives depletion (Zinc (Zn),Calcium (Ca)) presented a significant degradation in the case of CNG-HHO blend as compared to gasoline and CNG.Lubrication oil analyses illustrated 19.6%,12.8%and 14.2%decrease in average viscosity,flash point and TBN for CNG-HHO blend respectively.However,average water contents,Fe,Al and Cu mass concentration appeared 2.7%,25×10^(-6),19×10^(-6),and 22×10^(-6) in lubrication oil for CNG-HHO respectively.
基金Supported by the National Key Research and Development Plan(2016YFC0208005)the National Natural Science Foundation of China(51576016)
文摘The regulated gaseous emissions from 2 China-V compressed natural gas(CNG)buses and 2 China-V diesel buses were investigated using a portable emissions measurement system(PEMS)under real road driving conditions.Compared to diesel buses,CNG buses emit less NOx pollutants,but more HC and CO pollutants based on the test results obtained in this paper.In order to evaluate the pollutant emission status of CNG buses in Beijing,an instantaneous emission model as a function of vehicle speed and vehicle specific power(VSP)was developed and validated based on emission data taken from one CNG bus.The input of the instantaneous emission model consists of driving cycle,vehicle parameters,road conditions,ambient conditions and accessory use,all of which were used to calculate the instantaneous vehicle specific power(VSP).For the core model,a group of pollutant emission maps represented as functions of vehicle speed and VSP were used to calculate the second by second emission rates.Finally,the instantaneous emission rates,emission factors and fuel consumption over the selected driving cycle could be obtained as the model outputs.The predicted results for the emissions and fuel consumption of the CNG bus were very close to the tested emission data.The prediction errors for emission factors and fuel consumption varied in the range of-1.6 2%to-5.8%.
